1. Field of the Invention
This invention relates to a device for refilling or partially refilling a dual chamber dispensing cartridge used to contain and dispense two components of plural component material such as epoxies or dental impressioning material.
2. Description of the Related Art
Dual chamber dispensing systems are widely used for dispensing material that is made of two components or compositions. Examples of such material in the fields of construction and manufacturing include adhesives, coatings, sealants and potting compounds, while examples of such material in the medical field include dental impressioning material. Dual chamber dispensing systems often include a replaceable cartridge that has separate, side-by-side barrels with chambers that each hold one component of the material to be dispensed. Examples of dual chamber dispensing cartridges are described in U.S. Pat. Nos. 4,538,920 and 5,236,108.
Many dual chamber dispensing systems also include an applicator having a receptacle for removably receiving a dual chamber cartridge. Some applicators are adapted to be held by the hand during use, and include a pair of handles that, when squeezed together, simultaneously advance a pair of side-by-side plungers by means of a ratchet mechanism. As the plungers advance, the ends of the plungers contact respective pistons located in the chambers of the dispensing cartridge and move the pistons in a forwardly direction toward the front of the cartridge. As the pistons advance, the pistons expel the two components contained in both chambers simultaneously through respective outlets that are located near the front of the cartridge. Examples of hand-held applicators for dual chamber dispensing cartridges are described in EP Publication No. 0 539 074 A1, U.S. Pat. No. 5,137,181 and pending U.S. patent application Ser. No. 08/547,370 entitled "HAND-HELD APPLICATOR WITH FORCE LIMITING CLUTCH"
In some instances, and particularly in construction, manufacturing and industrial applications, electric or pneumatic operated applicators are used to dispense compositions from dual chamber dispensing cartridges. Electric applicators may be battery powered for convenient, hand-held manipulation, or instead may be powered by line current, a particular advantage when relatively large quantities of the components are to be dispensed. In areas where compressed air is readily available, air powered applicators may be preferred. Examples of powered dispensing applicators are described in U.S. Pat. Nos. 5,020,693, 5,064,098 and 5,080,493.
Dual chamber dispensing systems also often include a static mixer for mixing the components that are expelled from the cartridge. The static mixer includes an exit conduit that is detachably coupled to the front end of the cartridge and that communicates with the two spaced apart front outlets of the cartridge. A static mixing element is located within the exit conduit and includes a series of helical shaped mixing sections. When the plungers of the applicator are advanced to expel components from the cartridge, the components pass through the exit conduit where they are thoroughly mixed together by the successive mixing sections and then discharged through a front opening of the exit conduit, optionally directly to an application site. Examples of static mixers are described in U.S. Pat. No. 4,538,920 and PCT publication no. WO 95/22941.
In the dental arena, dual chamber dispensing systems are used to dispense two component impressioning material so that a model of the patient's teeth and gingiva can be obtained. In some procedures, the mixed impressioning material is dispensed into a dental impression tray that is then placed in the patient's oral cavity over selected teeth and gingiva. Once the material hardens, the tray is removed from the mouth and a model of the patient's teeth and gingiva is made by pouring a hardenable plaster of Paris solution, a resin or other molding material into the negative image formed in the impressioning material. After the molding material has hardened, the impressioning material is removed from the molding material in order to obtain a positive model of the patient's teeth and gingiva.
Dispensing cartridges are typically sold containing a larger quantity of impressioning material components than is expected to be needed to fill a typical tray. One reason that the cartridges contain a larger quantity of components than expected to be needed is due to the fact that the trays are available in a wide range of shapes and sizes, so that a particular tray can be selected to match the shape and size of the patient's dental arch that is encountered in practice. Manufacturers typically supply cartridges with a sufficient quantity of components to fill the largest expected tray. Consequently, unless the selected tray is unusually large, a quantity of the components often remains in the cartridge after the tray has been filled.
A dental impressioning dispensing cartridge that has been only partially emptied after a single use is sometimes used in a subsequent dispensing operation to place impressioning material in a second impression tray. However, a previously used cartridge often does not contain a sufficient quantity of the components to fill a second tray, and as a result the dispensing operation must be interrupted once the first cartridge is empty to replace the empty cartridge with a second cartridge. Unfortunately, there is often only a relatively short working time that is available for the practitioner to place and properly position the tray with the impressioning material in the oral cavity once the components are mixed and dispensed into the tray. If the dispensing operation is interrupted to remove an empty cartridge and install a full cartridge in the applicator, such an interruption necessarily reduces the amount of time available for the practitioner to place and properly orient the impression tray in the oral cavity.
As a consequence, many practitioners prefer to start with a new dispensing cartridge in the applicator each time that an impressioning tray is to be filled in order to avoid any reduction in the amount of time available to place and orient the tray in the oral cavity. Partially empty cartridges can be discarded, but such practice represents waste.
Similar problems exist in other fields where dual chamber dispensing cartridges are used. For example, when dispensing a fast-setting epoxy used in a manufacturing process, the user may not have sufficient time to replace an empty cartridge with a full cartridge during a dispensing operation. In such circumstances, the user may opt to start with a new cartridge at the beginning of each procedure, and discard any partially empty cartridges as waste.
Clearly, there exists a need in the art for a device that prevents such waste so that substantially all of the components in a cartridge can be used. Preferably, such a device would not interrupt a dispensing procedure so that the working time of the dispensed material is not reduced.